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Abstract:

The amount of ink wastage is reduced, even in a case wherein a
predetermined amount of air bubbles has grown in a print head at a
specific internal temperature and the growth has been settled, and
thereafter the temperature in the print head is increased. A
suction-based recovery control method, for an ink jet printing apparatus
that includes a print head, a temperature detection unit, and a
suction-based recovery unit, comprising: a temperature detection step; a
temperature judgment step for judging whether the internal temperature of
the print head is higher than a reference temperature that is determined
based on internal temperatures of the print head that were previously
employed; and a suction-based recovery step for permitting the
suction-based recovery unit when it is determined at the temperature
judgment step that the internal temperature of the print head is higher
by the predetermined number of degrees or greater.

Claims:

1. A suction-based recovery control method, for an ink jet printing
apparatus that includes a print head having a plurality of ejection ports
through which to eject ink droplets, a temperature detection unit for
detecting an internal temperature of the print head, and a suction-based
recovery unit for performing a suction-based recovery operation using
either first suction or second suction, the strength of which is stronger
than the first suction, in order to recover a state in which the print
head ejects ink droplets, comprising: a temperature detection step for
permitting the temperature detection unit to detect the internal
temperature of the print head; a temperature judgment step for judging
whether the internal temperature of the print head, detected by the
temperature detection unit, is higher, by a predetermined number of
degrees or greater, than a reference temperature that is determined based
on internal temperatures of the print head that were previously employed
when the suction-based recovery operation was performed; and a
suction-based recovery step for permitting the suction-based recovery
unit to perform the suction-based recovery operation using the second
suction, when it is determined at the temperature judgment step that the
internal temperature of the print head is higher by the predetermined
number of degrees or greater.

2. The suction-based recovery control method according to claim 1,
wherein the suction-based recovery operation performed by the
suction-based recovery unit is changed in accordance with a difference
between the internal temperature of the print head, detected by the
temperature detection unit, and the reference temperature.

3. An ink jet printing apparatus comprising: a print head having a
plurality of ejection ports through which to eject ink droplets; a
temperature detection unit for detecting an internal temperature of the
print head; a suction-based recovery unit for performing a suction-based
recovery operation using either first suction or second suction, the
strength of which is stronger than the first suction, in order to recover
a state in which the print head ejects ink droplets; a judgment unit for
judging whether the suction-based recovery unit is to perform the
suction-based recovery operation; and a temperature judgment unit for
judging whether the internal temperature of the print head, detected by
the temperature detection unit, is higher, by a predetermined number of
degrees or greater, than a reference temperature that is determined based
on internal temperatures of the print head that were previously employed
when the suction-based recovery operation was performed, wherein the
suction-based recovery unit performs the suction-based recovery operation
using the second suction, when the temperature judgment unit has
determined that the internal temperature of the print head is higher by
the predetermined number of degrees or greater.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a suction-based recovery control
method and an inkjet printing apparatus, and particularly relates to a
suction-based recovery control method and to an ink jet printing
apparatus, for detecting the temperature of a print head.

[0003] 2. Description of the Related Art

[0004] With an ink jet printing apparatus, it sometimes occurs that air
bubbles grow within ink paths and ink chambers, and during printing, are
carried along with the stream of ink to ejection nozzles, where they
interrupt the ejection of ink from the print head. To resolve this
problem, a known suction-based recovery technology has been applied to
periodically perform the mandatory removal of air bubbles, which have
grown in the print head, through the side where the ejection nozzles are
formed.

[0005] An example suction-based recovery control method is disclosed in
Japanese Patent Laid-Open No. 2010-052393, according to which, using a
control for timer suction-based recovery, a suction operation is
performed when a predetermined period of time has elapsed following an
immediately preceding suction operation, and the timing for suction-based
recovery is advanced as the temperature rises. This technique is provided
by focusing on the phenomenon that at higher temperatures, air bubbles
grow faster in ink paths.

[0006] However, it has been found through study, performed by the inventor
of the present invention, that when all of air bubbles have been
mandatorily discharged from the print head at a predetermined
temperature, almost no more air bubbles grow at that temperature. That
is, when the temperature rises by a predetermined number of degrees or
greater, beyond the temperature at which all the air bubbles were
discharged, i.e., the temperature at which the recovery process was
performed, air bubbles again begin to grow, and continue to grow until
the total number in the ink paths is once more sufficient to cause an
ejection failure, and to therefore require that the suction-based
recovery process be repeated.

[0007] Therefore, according to the method described in Japanese Patent
Laid-Open No. 2010-052393, whereby the suction-based recovery process is
advanced merely because the temperature is high, when air bubbles have
been mandatorily discharged while the print head is maintained at a high
temperature, the frequency at which suction is applied to increased, even
though no more air bubble growth occurs. As a result, the amount of ink
wastage is increased.

SUMMARY OF THE INVENTION

[0008] While taking this problem into account, one objective of the
present invention is to provide a suction-based recovery control method
and an ink jet printing apparatus, whereby the occurrence of an ejection
failure is not occurred and the amount of ink wastage is reduced, even in
a case wherein a predetermined amount of air bubbles has grown in a print
head at a specific internal temperature and the growth has been settled,
and thereafter the temperature in the print head is increased.

[0009] To achieve this objective of the present invention, a suction-based
recovery control method, for an ink jet printing apparatus that includes
a print head having a plurality of ejection ports through which to eject
ink droplets, a temperature detection unit for detecting an internal
temperature of the print head, and a suction-based recovery unit for
performing a suction-based recovery operation using either first suction
or second suction, the strength of which is stronger than the first
suction, in order to recover a state in which the print head ejects ink
droplets, comprising:

[0010] a temperature detection step for permitting the temperature
detection unit to detect the internal temperature of the print head; a
temperature judgment step for judging whether the internal temperature of
the print head, detected by the temperature detection unit, is higher, by
a predetermined number of degrees or greater, than a reference
temperature that is determined based on internal temperatures of the
print head that were previously employed when the suction-based recovery
operation was performed; and a suction-based recovery step for permitting
the suction-based recovery unit to perform the suction-based recovery
operation using the second suction, when it is determined at the
temperature judgment step that the internal temperature of the print head
is higher by the predetermined number of degrees or greater.

[0011] According to this structure, the suction-based recovery operation
is performed when the internal temperature of the print head exceeds, by
a predetermined number of degrees or greater, the highest temperature at
which the suction-based recovery operation was previously performed.
Therefore, even when the environmental temperature is raised, an ejection
failure does not occur due to the amount of air bubbles accumulated in
the print head, and the amount of ink wastage is reduced.

[0012] Further features of the present invention will become apparent from
the following description of exemplary embodiments (with reference to the
attached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a perspective view of a printing apparatus unit according
to one embodiment of the present invention;

[0014]FIG. 2 is a diagram illustrating a print head according to the
embodiment;

[0015] FIG. 3 is an exploded perspective view of the main body of the
print head according to the embodiment;

[0016]FIG. 4A is a perspective view, taken from one side face, of an
ejection recovery unit according to the embodiment;

[0017] FIG. 4B is a perspective view, taken from the side face opposite
the side face in FIG. 4A, of the ejection recovery unit;

[0018] FIG. 5 is a schematic block diagram illustrating the periphery of
the controller of the printing apparatus according to the embodiment;

[0019]FIG. 6 is a flowchart showing the control processing performed when
a temperature acquisition timer is counting up; and

[0020] FIG. 7 is a flowchart showing the control performed for the
suction-based recovery control operation according to the embodiment.

DESCRIPTION OF THE EMBODIMENTS

[0021] One embodiment of the present invention will be described in detail
while referring to the accompanying drawings.

[0022]FIG. 1 is a perspective view of a printing apparatus unit of an ink
jet printing apparatus according to the embodiment, with an exterior
member being removed. The printing section of a printing apparatus unit
2000 includes a carriage 2100 that is supported, at a carriage shaft
2103, so as to be movable, and a print head 4000 that is detachably
mounted on the carriage 2100 and that will be described in detail later
while referring to FIG. 2.

[0023]FIG. 2 is a diagram illustrating a print head according to the
embodiment. The print head 4000 for this embodiment includes ink tanks
4100 and a print head main body 4001. In this embodiment, black ink,
light cyan ink, light magenta ink, cyan ink, magenta ink and yellow ink
are stored respectively in the ink tanks 4100, and these ink tanks 4100
are detachably mounted to the print head main body 4001.

[0024] FIG. 3 is an exploded perspective view of the print head main body
4001 according to this embodiment. The print head main body 4001 of this
embodiment includes a printing element substrate 4010, a first plate
4020, an electric wiring board 4030, a second plate 4040, a tank holder
4050, an ink path forming member 4060, filters 4070 and rubber seals
4080.

[0025] On the printing element substrate 4010, a plurality of printing
elements for ejecting ink onto one side of a silicon substrate and
electrode wiring, such as aluminum wiring, to supply electric power to
the individual printing elements, are formed by the film deposition
technique. Further, a plurality of ink paths 4051 and a plurality of
nozzles that include ejection ports 4011 are arranged for the printing
element substrate 4010, in consonance with the printing elements, and an
ink supply port, for supplying ink to the ink paths 4051, is formed in
the reverse face. The printing elements employ thermal energy to eject
ink, and include electrothermal converters for generating thermal energy.
That is, thermal energy generated by the electrothermal converters is
employed to cause film boiling of ink, and based on the change of
pressure that occurs due to growing or shrinking of air bubbles, ink
droplets are ejected through the ejection ports 4011.

[0026] The ink path forming member 4060 is securely bonded, using
ultrasonic welding, to the tank holder 4050, where the ink tanks 4100 are
stored so as to be detachable, and provides the ink paths 4051 that serve
as channels for supplying ink from the ink tanks 4100 to the first plate
4020. Furthermore, the filters 4070 are located at the ends of the ink
paths 4051 that engage the ink tanks 4100, so that the entry of external
dust is prevented.

[0027] FIGS. 4A and 4B are perspective views of an ejection recovery
device 2200 for the printing apparatus according to the embodiment.
Specifically, FIG. 4A is a perspective view, taken from one side, of the
ejection recovery device 2200, and FIG. 4B is a perspective view, taken
from the opposite side, of this device 2200. The ejection recovery device
2200 is arranged outside the range wherein the carriage 2100, on which
the print head 4000 is mounted, reciprocates for the printing operation,
i.e., outside the printing area. The recovery process is performed in
order to maintain an appropriate ejection state for the print head 4000.
The ejection recovery device 2200 is positioned at a desired location
outside the printing area, such as the location correlated with the home
position for the carriage 2100 and the print head 4000. Further, the
ejection recovery device 2200 of this embodiment is arranged so as to be
independently detachable from the main body of the printing apparatus.
The ejection recovery device 2200 includes a wiping unit, for removing a
foreign substance from the printing element substrate 4010 of the print
head 4000, and a suction-based recovery unit, for obtaining the normal
state for the supply of ink along the ink paths 4051 from the ink tanks
4100 to the printing element substrate 4010 of the print head 4000.

[0028] The suction-based recovery unit includes: a cap 2206 that is made,
for example, of rubber and is used to cover the printing element
substrate 4010 of the print head 4000; an absorber 2207, provided inside
the cap 2206; and an arm 2208, that either brings the cap 2206 into
contact with, or separates the cap 2206 from the print head 4000.

[0029] The cap 2206 is supported by a holder that is provided separately
from the arm 2208, and this holder is held by the arm 2208. The cap 2206
is connected to a pump 2210 via a tube 2209, and when the pump 2210 is
operated, ink is drawn, by suction, from the print head 4000 that is
covered by the cap 2206. Another tube 2211 having an atmospheric
communicating valve 2212 is arranged en route between the cap 2206 and
the pump 2210.

[0030] The atmospheric communicating valve 2212 is formed, for example, of
a rubber based material, and an atmospheric communicating valve arm 2213
that is to be brought into contact with, or separated from, the
atmospheric communicating valve 2212, is provided at a shaft 2214 to be
rotatable in a direction indicated by D. When the pump 2210 is operated
while the atmospheric communicating valve arm 2213 is contacting the
atmospheric communicating valve 2212, the suction of ink from the print
head 4000 is performed. On the other hands, when the pump 2210 is
operated while the atmospheric communicating valve arm 2213 is separated,
the suction of ink from the print head 4000 is not performed, even though
the cap 2206 is in contact with the print head 4000, and only the ink
that is in the cap 2206 is drawn out by suction.

[0031] FIG. 5 is a schematic block diagram illustrating the periphery of
the controller of the printing apparatus according to this embodiment. A
controller 1 transmits an instruction for a suction-based recovery
operation to a suction-based recovery mechanism 2, and based on a count
value held by a temperature acquisition timer 4, transmits a temperature
acquisition instruction to a temperature detection sensor 2104. Then, the
controller 1 records, in a memory 3, the internal temperature reading for
the print head 4000.

[0032] The suction-based recovery mechanism 2 has a function for
performing an operation for removing air bubbles using second suction,
and a function for removing fixed adhesion ink and dust sticking to the
nozzles using first suction, and selects which operation is to be used in
accordance with the instruction received from the controller 1. The
temperature acquisition timer 4 is used to measure an elapsed time for
obtaining the internal temperature of the print head 4000, and begins
counting time after the second suction operation has been performed. When
printing is first begun or when suction-based recovery is begun after the
printing of a predetermined number of pages has been performed, or when
the time count value held by the temperature acquisition timer is 24
hours, the temperature detection sensor 2104 receives a temperature
acquisition instruction from the controller 1, and thereafter obtains the
internal temperature of the print head 4000.

[0033]FIG. 6 is a flowchart showing the control processing performed
while the temperature acquisition timer 4 is counting the elapsed time.
When the temperature acquisition timer 4 has counted the elapsed time
(step S201), a judgment is performed to determine whether the time count
value is 24 hours or more (step S202). When the time count value is less
than 24 hours, the control processing being performed, while the
temperature acquisition timer 4 is counting the elapsed time, is
terminated. When the time count value held by the temperature acquisition
timer 4 is 24 hours or more, an internal print head temperature TH
is obtained as a reference temperature T0 (step S203).

[0034] In this embodiment, the temperature acquisition time interval is
every 24 hours following the preceding performance of a second suction
operation. However, the temperature acquisition time for the present
invention is not limited to this time interval, and while taking the
bubble growth rate into account, any other time interval may be employed.
That is, when the interval for the temperature acquisition time is too
short, air bubbles might still be growing at the time of the detection of
the temperature rise, and therefore, the bubble growth rate must be taken
into account.

[0035] After the internal print head temperature TH is obtained (step
S203), a judgment is performed to determine whether the internal print
head temperature TH is higher by 7° C. or more than the
reference temperature T0 (step S204). When a temperature difference
between the internal print head temperature TH and the reference
temperature T0 is found to be smaller than 7° C., the count
value produced by the temperature acquisition timer 4 is reset, and the
control processing performed, while the elapsed time is being counted, is
terminated.

[0036] On the other hands, when the internal print head temperature
TH is higher by 7° C. or more than the reference temperature
T0, the reference temperature T0 is updated to the internal
print head temperature TH (step S205), and a second suction flag is
set to ON (step S206). Thereafter, the control processing performed while
the temperature acquisition timer 4 is counting the elapsed time, is
terminated. When the second suction flag has been set to ON during the
control processing performed while the temperature acquisition timer 4
was counting the elapsed time, a suction-based recovery operation, which
will be described later using FIG. 7, is performed.

[0037] It is assumed, for the print head 4000 of this embodiment, that in
a case wherein the internal print head temperature TH obtained at
the temperature acquisition time is higher by 7° C. or more than
the reference temperature T0 (the maximum temperature that the print
head 4000 can reach), there is a possibility that an ejection failure
will occur due to the growth of bubbles. However, a difference between
the internal print head temperature TH, which may adversely affect
ink ejection, and the reference temperature T0 varies, depending,
for example, on the members that form a print head, the composition of
ink, the lengths and diameters of ink paths and the shape of a liquid
chamber located immediately above the nozzles. Therefore, such a
difference factor should be determined in advance, based on the structure
for which the present invention is applied.

[0038] Furthermore, in the process at step S204, a temperature difference
between the internal print head temperature TH and the reference
temperature T0 has been employed to determine whether a
suction-based recovery operation should be performed. However, a
plurality of suction power levels maybe provided, and a suction level
maybe selected in accordance with a temperature difference between the
internal print head temperature TH and the reference temperature
T0.

[0039] In this embodiment, as described at step S204 and at step S106,
which will be described later, a difference between the temperature
TH of the print head 4000, detected by the temperature detection
sensor 2104, and the reference temperature T0, obtained at the
reference temperature acquisition step, is employed to determine whether
a suction-based recovery operation is to be performed.

[0040] FIG. 7 is a flowchart showing the suction-based recovery operation
performed for this embodiment. First, the controller 1 transmits, to the
suction-based recovery mechanism 2, either a suction instruction for an
automatic suction-based recovery operation performed when printing is
begun or when a predetermined number of pages have been printed, or a
suction operation instruction for an operation performed when a second
suction flag has been set to ON during the control processing using the
timer, as described while referring to FIG. 6, or a suction operation
instruction manually entered by a user (step S101). A judgment is then
performed to determine whether the suction operation instruction
transmitted by the controller 1 is for a suction operation performed
relative to the initial ink supply (step S102). A suction operation
performed relative to the initial ink supply is a suction-based recovery
operation for loading ink into the print head 4000 the first time, and
when the suction operation instruction is for a suction operation
performed relative to the initial supply of ink, the internal print head
temperature at that time is obtained, and recorded in the memory 3 as the
first reference temperature T0 (step S103). Then, the suction
operation relative to the initial supply of ink is performed (step S112),
the counting by the temperature acquisition timer 4 is started (step
S113), and the processing is thereafter terminated.

[0041] On the other hands, when the suction operation instruction is not
for a suction operation relative to the initial supply of ink (step
S102), the counting performed by the temperature acquisition timer 4 is
halted (step S104), and the internal print head temperature TH
immediately before the suction operation began is obtained (step S105).
Then, a judgment is performed to determine whether the internal print
head temperature TH obtained at step S105 is higher by 7° C.
or more than the reference temperature T0 (step S106).

[0042] When the internal printing head temperature TH is higher by
7° C. or more than the reference temperature T0, the
reference temperature T0 is updated to the internal print head
temperature TH (step S107). This is because, if air bubbles are
removed by suction at this temperature, a rapid growth of bubbles will
not occur due to an increase in the temperature unless the current
temperature is updated.

[0043] When the internal print head temperature TH is higher by
7° C. or more than the reference temperature T0, it is highly
probable that the number of air bubbles generated in the print head 4000
has already reached a level that causes an ejection failure, and that
therefore, a second suction operation is required, regardless of whether
a first or a second suction operation instruction was issued at step
S101. Therefore, the level for a suction operation has been determined
(step S108), and when an instruction for a second suction operation has
already been issued, the suction level is unchanged, while when an
instruction for a first suction operation has been issued, the suction
level is changed to second (step S110).

[0044] In the process at step S110 for judging the suction-based recovery
operation, several suction levels may be provided, and a suction level
may be selected based on a temperature difference between the internal
print head temperature TH and the reference temperature T0.

[0045] When the suction level is changed to second suction (step S110), or
when a second suction operation has been designated (step S108), the
count value for the temperature acquisition timer 4 is reset, and the
suction operation is started (step S112).

[0046] When a judgment is performed to determine whether the internal
print head temperature TH is higher by 7° C. or more than the
reference temperature T0 (step S106), and when the temperature
difference between the internal print head temperature TH and the
reference temperature T0 is determined to be smaller than 7°
C. (S111), the level of suction is subsequently examined. When the level
of suction is second, the count value for the temperature acquisition
timer 4 is reset (step S109), and the suction operation is performed
(step S112). However, when the level of suction is first (step S111), the
count value of the temperature acquisition timer 4 is not reset, and the
suction operation is performed (step S112).

[0047] After the suction operation has been performed, the counting by the
temperature acquisition timer 4 is started (step S113), and thereafter
the suction-based recovery operation for this embodiment is terminated.

[0048] As described above, in this embodiment, when the internal
temperature of the print head is higher by a predetermined number of
degrees or greater than the temperature when the suction-based recovery
operation was previously performed, the suction-based recovery operation
is performed. Therefore, when the environmental temperature is increased,
an ejection failure does not occur because of the amount of air bubbles
that have accumulated in the print head, and the amount of ink wastage
can be reduced.

[0049] While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is not
limited to the disclosed exemplary embodiments. The scope of the
following claims is to be accorded the broadest interpretation so as to
encompass all such modifications and equivalent structures and functions.

[0050] This application claims the benefit of Japanese Patent Application
No. 2010-281812, filed Dec. 17, 2010, which is hereby incorporated by
reference herein in its entirety.

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Patent applications in class Of temperature or pressure of device or component thereof

Patent applications in all subclasses Of temperature or pressure of device or component thereof